1. Field of the Invention
The present invention relates to a method and apparatus for waterproofing a wire harness, such as one disposed in the boundary between an engine compartment and vehicle interior, where prevention of water penetration is necessary.
2. Description of the Related Art
When placing a wire harness in the boundary between the engine compartment of a vehicle and the interior, prevention of water penetration is necessary. Conventionally, as shown in FIG. 1, a grommet 2 fixed to a main wire portion of a wire harness 4 is mounted in a through-hole of a partitioning plate 1 disposed between the engine compartment of the vehicle and the interior to prevent the penetration of water into the gap therebetween. In such an arrangement, a sheet 3 may be wound on a grommet-engaging portion of the wire harness 4. Water penetrates into the gap between the wire harness 4 and the sheet 3, as well as gaps between electric wires 5 constituting the wire harness 4, if the gaps are empty. In order to prevent water penetration, filler 6, such as silicon, is filled between the wire harness 4 and the sheet 3, and the gaps between electric wires 5.
A waterproofing method which includes filling the filler 6 into the gaps between the electric wires 5 is disclosed in Japanese Patent Application Laid-Open No. 2000-114746. In this method, as shown in FIGS. 2A and 2B, a plurality of electric wires 5 constituting the wire harness 4 are flattened, the electric wires 5 are arranged in close contact with each other and fixed between two electric wire-supporting tools 8, and the filler 6 is applied to each of the arranged electric wires 5. As shown in FIG. 3, the filler-applied flattened electric wires 5 are next arranged in a sectionally circular bundle, and finally the bundle is covered with the sheet 3.
In the above-described method, the filler is merely applied to the surface of each of the electric wires 5 arranged in close contact with each other. Thus, the filler does not penetrate into the gaps between the electric wires 5 arranged in close contact with each other. Therefore, when the electric wires 5 are thereafter arranged in a sectionally circular bundle, there is the potential for fillerless gaps 7 to be generated.
Thus, if the filler has a high viscosity, there is a high possibility that a gap 7 devoid of filler will be generated. Further, improvement of the filler-filled condition after the sheet 3 is wound around the bundle of the electric wires 5 is limited. Thus, it is impossible to provide a wire harness having reliable waterproof performance.
The present invention has been made in view of the above-described problems. Accordingly, it is an object of the present invention to provide a method and an apparatus for waterproofing a wire harness, which is capable of accelerating spreading and penetration of a filler after a sheet is wound around a bundle of electric wires to achieve an enhanced waterproofing performance.
To achieve the foregoing object, according to the present invention, a method for waterproofing a wire harness is provided that includes providing a wire harness having a plurality of electric wires, applying a filler to the electric wires at a predetermined waterproofing portion of the wire harness, winding a sheet around a peripheral surface of the bundled electric wires to which the filler has been applied, and pressing the sheet covered waterproofing portion of the wire harness to produce spreading and penetration of the filler into gaps between the sheet and the electric wires and gaps between the electric wires themselves.
According to the method of the present invention, the bundle of electric wires is pressed inward from the outer side of the sheet after the sheet is wound around the portion to which the filler is applied. Therefore, it is possible to displace the electric wires and the filler relative to each other and accelerate the penetration of the filler filled in the waterproofing portion and enclosed within the sheet into the gaps between the sheet and the electric wires and the gaps between the electric wires themselves.
The present invention also includes a wire harness having a waterproofing portion formed according to such a method.
In a further aspect of the present invention, the sheet covered waterproofing portion of the wire harness is initially pressed in a first radial direction, and thereafter pressed in a second radial direction. The first radial direction may be substantially perpendicular to the second radial direction. The pressing may further include repeatedly patting the sheet covered waterproofing portion of the wire harness.
In a further aspect of the present invention, the waterproofing portion is pressed while the wire harness is continuously fed along a feed path.
Further, in the method according to the present invention, the waterproofing portion of the wire harness is radially pressed by a clamping mechanism, and a pressing position of the waterproofing portion is altered by a rotation mechanism that rotates the clamping mechanism about an axis of the waterproofing portion. The clamping mechanism may be rotated by an amount so that a pressing direction after rotation is substantially perpendicular to a pressing direction prior to rotation. Further still, the waterproofing portion may be pressed by the clamping mechanism, and the clamping mechanism may be rotated by the rotation mechanism, while the wire harness is continuously fed along a feed path.
In another aspect of the present invention, there is provided an apparatus for waterproofing a wire harness that includes a clamping mechanism configured to clamp a waterproofing portion of a bundle of electric wires of a wire harness so that the bundle is pressed in a radial direction thereof, the waterproofing portion having a sheet wound around the bundle of electric wires and a filler for sealing gaps between the electric wires and the sheet. The apparatus includes a rotation mechanism configured to rotate the clamping mechanism about an axis of the waterproofing portion, and a controller that controls operation of the clamping and rotation mechanisms. The controller controls the clamping and rotation mechanisms so that at predetermined time intervals, the rotation mechanism alters a pressing position of the waterproofing portion by rotating the clamping mechanism relative to the waterproofing portion.
In this aspect of the present invention, because the clamping mechanism clamps a sealed portion of the bundle of electric wires, the sealed portion deforms radially, and the rotation mechanism circumferentially alters the pressing position of the waterproofing portion to be pressed by the clamping mechanism. Therefore, the sealed portion of the bundle of electric wires is massaged by the clamping mechanism, which accelerates the spreading and penetration of the filler filled into the waterproofing portion into the gaps between the sheet and the electric wires and the gaps between the electric wires themselves.
In a further aspect of the present invention, the clamping mechanism is substantially U-shaped and includes opposing arms configured to receive the waterproofing portion therebetween. The clamping mechanism repeatedly pats the waterproofing portion.
It is preferable that the rotation mechanism includes an introduction groove containing gear connected with the clamping mechanism for rotation therewith and having an introduction groove configured to receive the waterproofing portion therein, and a driving mechanism including an output gear configured to engage and drive the introduction groove containing gear to rotate the clamping mechanism about the axis of the waterproofing portion. In this case, the pair of power transmission gears (introduction groove containing gear and output gear) of the driving mechanism can rotate the clamping mechanism easily in the circumferential direction of the waterproofing portion. Further, the introduction groove containing gear may be driven by an amount so that a pressing direction after rotation of the clamping mechanism is substantially perpendicular to a pressing direction prior to rotation of the clamping mechanism.
In still another aspect of the present invention, the rotation mechanism and the clamping mechanism are mounted on a conveyor line for feeding the wire harness in such a way that a hand unit carrying the rotation mechanism and the clamping mechanism is moved by a movement mechanism that allows the hand unit to move in the wire harness-feeding direction so that the rotation mechanism and the clamping mechanism follow the movement of the waterproofing portion of the wire harness along the conveyor line. The movement mechanism moves the clamping mechanism and rotation mechanism in the downstream direction at the same speed as that of the wire harness.
In this case, when the waterproofing portion of the wire harness is waterproofed by the rotation mechanism and the clamping mechanism, the waterproofing portion can be pressed, with the wire harness being moved on the conveyor line. Thus, it is possible to waterproof the wire harness automatically on the conveyor line.
In a further aspect of the present invention, a detector is provided for detecting a position of the wire harness along the feed path. The detector may detect a leading edge of an assembly board on which the wire harness is fed along the feed path. The movement mechanism moves the clamping mechanism downstream in response to a signal from the detector.
In another aspect of the present invention, an apparatus for waterproofing a wire harness is provided which includes a clamping mechanism configured to clamp a waterproofing portion of a bundle of electric wires of a wire harness so that the bundle is pressed in a first radial direction thereof, the waterproofing portion including a sheet wound around the bundle of electric wires and a filler for sealing gaps between the electric wires and the sheet. The apparatus also includes a rotation mechanism configured to rotate the clamping mechanism about an axis of the waterproofing portion so that the clamping mechanism presses the bundle in a second radial direction thereof.